Miguel Cotto claimed a unanimous points decision over Sugar Shane Mosley to retain the WBA welterweight title at Madison Square Garden on Saturday.
Cotto (right) lands with a clubbing right-hand against Mosley
The victory means the Puerto Rican is in line to face the winner of next month's super-fight between Britain's Ricky Hatton and Floyd Mayweather.
Two judges scored the fight 115-113 and a third had it 116-113 for the holder.
It meant the 27-year-old improved his record to 31-0 and also took the WBC interim crown from veteran Mosley, 35.
Former three-weight world champion Mosley has beaten fellow Americans Oscar de la Hoya and Fernando Vargas twice and rolled back the years to outclass Luis Collazo for the WBC interim belt in February.
But unlike Cotto, who has climbed into the ring 13 times over the last four years, this was just his eighth bout in the same time span.
And the champion did enough in a battle that never quite reached epic proportions of his previous defence against Zab Judah but was still an exciting clash of styles.
The fight really came alive at the end of the second round when Mosley caught the champion with a big right, provoking an immediate response from Cotto as they traded furious blows over the final 30 seconds.
I knew I had a big lead, but Shane punches real hard and I was hurt
Cotto stepped it up a gear in the sixth as he repeatedly landed shots on Mosley's head and chin without significant response.
But Mosley rallied in the seventh and at the start of the 10th stormed out of his corner to have Cotto in trouble on the ropes.
The 11th was just as relentless, Mosley working the body before Cotto broke out in the final 10 seconds to hurt his man at the bell.
The final round still gave both fighters everything to box for, although Mosley went down in the champion's corner, but only with a slip.
But despite sustaining a cut above his eye through a clash of heads, Cotto had done enough to keep his title in front of over 15,000 adoring fans in the legendary New York venue where he has now carded four straight wins.
"That's what I trained to face and I thought I did real well. I wanted to give my best performance for the fans and I thought I did," Cotto said.
"I knew I had a big lead, but Shane punches real hard and I was hurt."
Mosley added: "Miguel was very strong, not only was he a powerful puncher but he can box. He mixed it up and did a hell of a good job. He's a young lion on the way to greatness."